Encyclopedia Smithsonian: Moths

Moths

Arctiidae: Pericallia galactina, Malaya
Smithsonian photo by Kjell B. Sandved.
(c) 1999 Smithsonian Institution. Not to be reproduced without written permission.

Numbers of species. Moths are in the insect Order Lepidoptera, and share this Order with Butterflies. There are some 160,000 species of moths in the world, compared to 17,500 species of butterflies. In the United States, there are nearly 11,000 species of moths.

Distinctive characteristics. Moths (and their close relatives, the butterflies) are the only group of insects that have scales covering their wings, although there are a few exceptions. They differ from other insects also by their ability to coil up their feeding tube (the proboscis). Moths can usually be distinguished from butterflies by their antennae, which are typically threadlike or feathery; in contrast, butterflies have club-tipped antennae.

General statements. Although moths have for the most part relatively dull wing colors, there are many species with spectacular colors and patterns. The Giant Silkworm Moths form a vast array of large, impressive insects with colorful wings, sometimes with long tails on the hind wings. One of the moth species most commonly seen is the Tomato Hornworm Moth, although it is noticed in the caterpillar stage as it devours tomato foliage in the garden. Opposite to the habits of butterflies, moths usually fly during the night to gather nectar at flowers. However, there are many day-flying moths, and many of them are brightly colored. The insect that is often considered as the most beautiful insect in the world is a day-flying moth, The Sunset Moth, from Madagascar. Day-flying moths are often noticed feeding at flowers.

Immatures. Caterpillars are the name given to the larvae of both moths and butterflies. They are usually very distinctive, and in some cases may be identified more easily than the adults. Caterpillars eat voraciously to transform plant material into the tissues that they will need for changing into moths.

Migration in the Lepidoptera is not limited to butterflies such as the Monarch. There are many migratory moths, including the day flying Hummingbird Hawkmoth, which migrates from southern parts to northern parts of Europe as temperatures rise in early summer.

Evolution example. The Peppered Moth of Europe is commonly cited as a classic example in evolution, and was studied by H. B. D. Kettlewell as an example of "industrial melanism. Moths with salt and pepper colored wings are not detected on bark that contains lichens of similar colors and patterns. Trees during the industrial revolution became so soot-covered that moths with genetic makeup for dark colors developed because they were not seen and eaten by birds. The reverse of this mechanism has resulted through time as tree bark returned to a lighter color.

Arctiidae; Hyperthaema sanguineata (Moth Manaus, Amazonas) Smithsonian photo by Kjell B. Sandved. (c) 1999 Smithsonian Institution. Not to be reproduced without written permission.

Classification. Moths are divided into many families that have different morphological characteristics. The following families include the majority of moth species:

Arctiidae. There are approximately 10,000 species of this Family in the world, and they are commonly called Tiger Moths. Many species in this group display bright colors of red and yellow.

Geometridae. With some 15,000 described species, this Family is the second largest of moths in the world. Larvae are usually called "inch-worms" because of their walking patterns.

Noctuidae. This Family is by far the largest in moths, with some 25,000 known species in the world. Cutworms, fruitworms and underwing moths occur in this Family.

Saturniidae. This Family includes the largest of moths, and incorporates some 1,000 worldwide species. The Luna Moth of the Eastern United States is an example of this Family.

Sphingidae. Members of this Family have streamlined wings and robust bodies. They are generally large, and the Family contains about 1,000 species.

Microlepidoptera is the term given to a wide variety of very small moths (with few exceptions). The group contains many thousands of tiny species, some with spectacular colors and appearances. Some are pest species, such as the Clothes Moth and the Codling Moth.

Selected References:

Carter, David. 1992. Butterflies and Moths (Eyewitness Handbooks). Dorling Kindersley, Inc., New York.

Covell, C. V., Jr. 1984. A Field Guide to the Moths of Eastern North America. Houghton Mifflin, Boston.

Hodges, R. W. 1971. The Moths of America North of Mexico. Fascicle 21: Sphingoidea. Curwen Press, London. (This is one of many volumes in the M.O.N.A. series, an ongoing project of major importance).